Yoga has undergone much scientific study, with various psychological and physical theories suggested. In human research, yoga has been shown to reduce heart rate and blood pressure, increase breath holding time and lung capacity, improve muscle relaxation and body composition, cause weight loss, and increase overall physical endurance. Yoga may positively affect levels of brain or blood chemicals, such as monoamines, melatonin, stress hormones (cortisol), and GABA (gamma aminobutyric acid). Changes in several mental functions, including perception, attention, cognition, processing of sensory information, and visual perception, are described in human research.

It is proposed that health may be affected by mind-body interactions that occur through techniques such as yoga, and that daily practice of yoga may help to maintain wellness.

Evidence

DISCLAIMER:
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

High blood pressure:
Several human studies support the use of yoga in the treatment of high blood pressure when practiced for up to one year. It is not clear if yoga is better than other forms of exercise for blood pressure control. Yoga practitioners sometimes recommend that patients with high blood pressure avoid certain positions, such as headstands or shoulder stands (inverted asanas), which may increase blood pressure.
Grade: A

Altitude sickness:
Yoga uses controlled breathing patterns to increase breathing efficiency. More research is needed before a recommendation can be made.
Grade: B

Anxiety:
Several human studies support the use of yoga therapy in the treatment of clinical anxiety disorders and in otherwise healthy individuals with anxiety. Additional well-designed studies are needed before a strong recommendation can be made.
Grade: B

Arthritis:
There is promising early evidence that yoga therapy may help treat both osteoarthritis and rheumatoid arthritis. More research is needed to confirm these results.
Grade: B

Asthma:
Multiple human studies report benefits of yoga (such as breathing exercises) when added to other treatments for mild-to-moderate asthma (such as standard drug therapy, diet, or massage). Better research is needed before a firm conclusion can be drawn.
Grade: B

Carpal tunnel syndrome:
Yoga therapy has been studied for carpal tunnel syndrome, but it is not clear if there are beneficial effects. Further research is needed before a recommendation can be made.
Grade: B

Depression:
Several human studies support the use of yoga for depression in both children and adults. Although this preliminary research is promising, better studies are needed.
Grade: B

Heart disease:
Several human studies suggest that yoga is helpful in people with heart disease. However, it is not clear if yoga reduces the risk of heart attack or death or if yoga is better than any other form of exercise therapy or lifestyle/dietary change. Therefore, yoga may be a useful addition to standard therapies (such as medications for blood pressure or cholesterol) in people at risk for heart attacks, but further research is necessary before a strong recommendation can be made.
Grade: B

Lung disorders:
Limited adult human study exists for the treatment of lung conditions such as bronchitis, fluid around the lungs (pleural effusion), or airway obstruction. Better-designed research is necessary before any firm recommendations can be made.
Grade: B

Obsessive-compulsive disorder:
Several human studies support the use of yoga therapy in the treatment of obsessive-compulsive disorder (OCD). Additional well-designed studies with clearly defined patient groups are needed before a strong recommendation can be made.
Grade: B

Quality of life:
Yoga may be beneficial for improving the quality of life for patients with serious diseases as well as in healthy patients. Several studies in cancer patients report enhanced quality of life, lower sleep disturbance, decreased stress symptoms, and changes in cancer-related immune cells after patients received relaxation, meditation, and gentle yoga therapy. Higher quality studies are needed.
Grade: B

Schizophrenia:
Several human studies support the use of yoga therapy in the treatment of schizophrenia. Additional well-designed studies with clearly defined patient groups are needed before a strong recommendation can be made.
Grade: B

Seizure disorder (epilepsy):
Several human studies report a reduction in the number of monthly seizures with the use of Sahaja yoga, when it is added to standard anti-seizure drug treatment or a yoga meditation protocol. This research is preliminary and better studies are necessary before a firm conclusion can be drawn.
Grade: B

Substance abuse:
Preliminary research suggests that yoga may be beneficial when added to standard therapies for the treatment of heroin or alcohol abuse. Additional studies are needed before a strong recommendation can be made.
Grade: B

Attention deficit hyperactivity disorder (ADHD):
There is limited study in humans of yoga in the treatment of attention deficit hyperactivity disorder (ADHD). Further research is needed before a recommendation can be made.
Grade: C

Diabetes:
Several preliminary human studies suggest that daily yoga may improve control of blood sugar levels in people with type 2 diabetes when it is added to standard drug therapy. It is not clear if yoga is better than any other form of exercise therapy. Better research is needed before a recommendation can be made.
Grade: C

Eating disorders:
There is unclear evidence in this area.
Grade: C

Fatigue:
Preliminary studies in humans report that yoga may improve fatigue in adults. However, better-designed studies are needed before any conclusion can be made.
Grade: C

Headache:
Preliminary evidence suggests that yoga may effectively reduce the intensity and frequency of tension or migraine headaches and lessen the need for pain-relief medications. Better studies are needed before a recommendation can be made.
Grade: C

Insomnia:
Preliminary research reports that yoga may benefit sleep efficiency, total sleep time, number of awakenings, and quality of sleep. Well-designed research is necessary before a firm recommendation can be made.
Grade: C

Irritable bowel syndrome (IBS):
Early evidence suggests that yoga may be beneficial in the management of IBS. Further research is needed to make a recommendation.
Grade: C

Memory:
There is limited human study of yoga to improve memory. Most research focuses on memory in children. Better studies are needed before a recommendation can be made.
Grade: C

Menopausal symptoms:
Early evidence showed mixed results regarding yoga's effect on menopausal symptoms. Although early results are promising, more research is needed in this area.
Grade: C

Mental retardation:
There is limited human study of yoga therapy in children with mental retardation. Better trials are needed to confirm these results and to evaluate the effects of yoga in mentally retarded adults.
Grade: C

Multiple sclerosis (fatigue, cognitive function):
There is limited study of yoga therapy in patients with multiple sclerosis. Further research is needed before a recommendation can be made.
Grade: C

Muscle soreness:
There is limited study in humans of yoga for improving muscle soreness. Further research is needed before a recommendation can be made.
Grade: C

Pain:
Preliminary research reports that yoga may improve chronic low back pain in humans. However, larger better-designed studies are needed before a firm conclusion can be drawn.
Grade: C

Performance enhancement:
Preliminary studies in humans report that yoga (mukh bhastrika) may improve human reaction time, arousal, information processing, running performance, and concentration. Further research is needed before a clear recommendation can be made.
Grade: C

Pregnancy:
Early research suggests yoga during pregnancy is safe and may improve outcomes. Additional research is needed before a clear recommendation can be made. Pregnant women who wish to practice yoga should discuss this with their obstetrician or nurse-midwife.
Grade: C

Ringing in the ears (tinnitus):
It is unclear whether yoga therapy may improve tinnitus. Although relaxation may theoretically benefit this condition, additional research is needed before a recommendation can be made.
Grade: C

Slow (delayed) ejaculation:
There is early evidence to support the use of yoga in the treatment of delayed ejaculation in males. Larger well designed and controlled trials are needed to further assess the effects of yoga for sexual health.
Grade: C

Stroke:
Preliminary study suggests possible benefits of a yoga-based exercise program on people who have had a stroke and have impaired health status and reduced level of activity. Although results seem promising, further well-designed research is needed to confirm these findings.
Grade: C

Weight loss/obesity:
Preliminary research does not provide clear answers. Yoga in addition to healthy eating habits may reduce weight. Better studies are necessary to form conclusions about the potential benefits of yoga alone.
Grade: C